When a metal is machined by operating a cutting machine such as a lathe, drilling machine or the like, or a grinding machine such as a surface grinding machine, external cylindrical grinding machine or the like, there are produced cuttings in the form of coil or powder. The cuttings are industrial waste and hence, a demand exists for processing the cuttings into a shape as compact as possible for easy transportation. In this connection, compactors have been developed and marketed which produce high-density solid products by compacting the cuttings.
The compactor is arranged such that the cuttings fed from a hopper are delivered by a screw conveyor to a compaction chamber of a cylindrical body having a circular or rectangular section; and that the cuttings in the compaction chamber are compacted into a solid product by means of a hydraulic cylinder and then a movable gate member disposed at one end of the compaction chamber is opened so as to discharge the solid product of the compacted cuttings out of the compaction chamber. In some cases, a pressing force applied to the cuttings by the hydraulic cylinder may exceed 40 tons so that the cylindrical body constituting the compaction chamber may be subject to a pressure in excess of 1000 kgf/cm2. This involves a problem that the gate member becomes hard to open because of a pressing force from the solid product thus formed and a frictional force between the solid product and an inside wall of the compaction chamber. As a solution to the above problem, the inventors have developed a compactor wherein the cylindrical body includes an outside cylinder and an inside cylinder axially movably accommodated in the outside cylinder, and then have acquired the right to a patent (U.S. Pat. No. 2,949,664).
The above compactor is often used for compacting abrasive dusts and small-particle metallic residues (sludge) produced during a metal polishing process. The sludge contains abrasive grains which are dusts from an abrasive stone. The metal polishing process employs a variety of polishing materials according to the types of metals to be polished. Main polishing materials include alumina oxide abrasive grains, silicon carbide abrasive grains, CBN (cubic boron nitride) abrasive grains, diamond abrasive grains and the like. It is known that the alumina oxide abrasive grains are used in greater quantities.
In the aforementioned abrasive grains, even the alumina oxide abrasive grains of the lowest Knoop Hardness (HK) have a hardness on the order of 1950 to 2050, which is higher than a Knoop Hardness (1700–1940) of a sintered hard alloy. It was found that because of the pressing force for forming the solid product as well as the frictional force between the solid product and the inside wall of the compaction chamber, an inside wall portion near an end of the compaction chamber is worn seriously during the compaction of the sludge containing the abrasive grains.
The wear on the inside wall of the compaction chamber results in a solid product having an increased outside diameter at an axially intermediate portion thereof. This leads to a problem that the solid product cannot be discharged although the solid product is pushed by the hydraulic cylinder after the gate member is opened. When such a problem is encountered by the conventional compactor, a measure to be taken by the current practice is to replace the worn cylindrical body.
Unfortunately, in the arrangement wherein the compaction chamber consists of a single cylindrical body, it is difficult, by definition, to replace the cylindrical body itself. Even in the arrangement wherein the cylindrical body consists of the outside cylinder and the inside cylinder accommodated therein, the replacement requires considerable cost and time because the inside cylinder has a length to cover a distance from a rearward position of a cylinder rod of the hydraulic cylinder to the gate member. For instance, the existing state is such that a number of service workers take a number of hours to disassemble the gate member and hydraulic cylinder of the compactor and to replace the inside cylinder. There is another problem that experience is required to adjust the position of the inside cylinder relative to the cylinder rod because the inside cylinder extends to the rearward position of the cylinder rod.
It is an object of the invention to provide a compactor permitting the worn cylindrical body constituting the compaction chamber to be replaced by a low-cost and relatively simple operation.